Numerical analysis of Pt utilization in PEMFC catalyst layer using random cluster model

A random cluster model was proposed to simulate the catalyst layer of PEMFC. The cluster model consists of a random distribution of three kinds of particles, i.e., Pt/C catalyst, Nafion and poly-tetra-fluoro-ethylene (PTFE), which were generated on a computer by means of Monte Carlo method. Based on such a cluster model, the catalyst utilization was calculated through counting the number of Pt/C clusters and Nafion particles clusters. It was assumed that the effective Pt/C clusters are those that not only have electron channels via carbon particles to current collector but also have proton channels via Nafion polymer particles to the Nafion membrane. The factors influencing catalyst utilization was thoroughly discussed. For the case of high catalyst utilization, numerical results showed that there is a threshold for ratio of Pt/C catalyst loading to Nafion. Beyond this threshold, the catalyst utilization may drop dramatically. The results also showed that the Pt/C catalyst with higher Pt content could allow a larger range of the ratio of the Pt/C catalyst loading to Nafion. Generally, there is high catalyst utilization around the ratio of 1. Results also showed that the lower the Teflon loading in the catalyst layer, the higher the catalyst utilization will be. However, the Pt/C catalyst with higher Pt content can tolerate relatively high Teflon loading than that with a lower Pt content.